This study presents a method for fabricating customized insoles using fused filament fabrication (FFF) and user-specific foot shape data. We evaluated the method's effects through plantar pressure distribution and Arch Index (AI) analysis. To capture plantar contours, we designed a kit-type impression-based acquisition process. The resulting impressions were digitized using three-dimensional (3D) scanning. We aligned the scanned plantar impression with a base insole CAD model, iteratively modifying and verifying the upper surface to reconstruct a customized insole geometry. The final insole model was exported in STL format and produced using FFF with a thermoplastic polyurethane (TPU) filament and a 25% honeycomb infill structure. A subject with a high arch wore the customized insoles during daily activities for one month, with plantar pressure data collected three times before and after the wear period. After using the customized insoles, the midfoot contact area increased from approximately 10–15% to 20–25% of the total plantar contact area, and the plantar load distribution shifted from a forefoot-rearfoot concentration to a more balanced pattern. These results demonstrate that the proposed FFF-based customized insole effectively enhances medial arch support and promotes a balanced plantar load distribution.
